A number of specialised pieces of equipment are used in the construction and operation of wells. These specialised pieces of equipment include various types of rigs. A drill rig is used to drill the well. A work-over or intervention rig is used to rotate rods into the well to complete the well. A flushby rig is used to flush debris from the well.
During maintenance and repair works, a flushby rig may be used to flush the well. When flushing has failed to re-establish production from a well and the well needs intervention to bring the well back into production, the practice is to remove the flushby rig and set up a larger workover/intervention rig. The workover/intervention rig performs work and drills with the rods. After the workover/intervention rig has completed its work, it is removed and the flushby rig returns to the well to flush out the well.
The process of exchanging rigs uses considerable time. Currently, intervention rigs can take up to 6 hours to setup and up to another 4 to 5 hours to take down.